Description: (Adapted from the application) This revised application aims to apply Dr. Caffrey's expertise in lipids to the rational design of cubic lipid phases for the crystallization of membrane proteins. Though a number of membrane proteins, notably bacteriorhodopsin (BR), have been successfully crystallized from lipid cubic mesophases, there has been no careful study of the optimum state of the mesophase, and of the details of the boundary between the growing crystal and the bulk phase. Instead only empirical procedures are used to obtain crystals. To remedy this, Dr. Caffrey proposes to extend his library of phase diagrams for monoacylglycerols, which form cubic mesophases, and to study the relationship between the phase diagrams and the optimum crystallization of BR and of a bacterial photoreaction center, RC. The results of these studies, together with an analysis in detail of the crystal/lipid interface will then be used in attempts at rational crystallization of the previously uncrystallized photosystem II from Chlamydomonas.